This invention relates generally to magnetic recording tape reels. More particularly, the present invention relates to a tape reel that reduces print through errors on data tape wound onto the reel when used in association with a buckle between the take-up leader and the supply leader.
Magnetic tapes are used for data storage in computer systems requiring data removability, high data rate capability, high volumetric efficiency, and reusability. The use of magnetic tape data storage devices is commonplace, as the cost per unit of stored data is low compared to other forms of electronic data storage, and magnetic tape devices are frequently used to back-up or preserve data stored on more expensive-non-removable disk drives.
Magnetic tape formats include open reels, tape cartridges and cassettes. In the past, it was common to use a simple open reel including a hub upon which the tape was wound and flanges that protect the edges of the tape. However, the need for additional tape protection and a desire for a reduction in the need for human intervention in installing or replacing data tapes in tape data storage devices has led to the increased use of tape cartridges and cassettes. A typical magnetic tape includes a polymer film substrate with a coating of magnetic recording material on one side, and a non-stick coating of material on the other side to reduce adhesion between layers of tape wound on a reel. In a typical tape drive using tape cartridges, the tape runs between a rotatable supply reel housed within the tape cartridge and a take-up reel in the tape drive assembly. When the cartridge is inserted into the tape drive, a take-up leader on the take-up reel is coupled to the supply leader, which is further coupled to the tape on which the data is stored. The procedure of coupling the take-up leader to the supply leader is known as buckling. Once the two leaders are coupled, the data tape is pulled through the tape path to the take-up reel by the take-up leader.
There is an increasing need for tape data storage devices that provide greater data storage capacity and higher data transfer rates. To satisfy the requirement for data storage, higher track densities on the magnetic tape are sought. The greater the track density, the greater the volume of information that may be stored on the tape. Accordingly, the width of tracks and separation between tracks has continued to decrease in order to accommodate more data tracks. However, as data tracks narrow, the signal strength from the tracks decreases. Therefore, even minor magnetic influences can mask or distort the magnetic data on a data tape sufficiently that data is lost.
There are a variety of sources of such data errors or losses. One source of data error is called print through, which results when non-uniform pressure distribution is applied to tape media as it resides on the reel. Print through is the tendency of the magnetic information stored on a layer of tape to be influenced by the magnetic data stored on an adjacent layer of tape, but will be used herein to include embossing sources of error as well. Magnetic tape in tape drives may be wound tightly. For example, in DLT(trademark) tape drives made by Quantum Corporation, magnetic tape wound on a reel may experience pressure between 200-400 psi towards the central axis of the reel. Experimental results have shown that even small deviations from circularity of the reel may cause localized pressures experienced by the magnetic tape to exceed 1,000 psi. The non-magnetic layer of most tape, which may normally be relied on to minimize print through, is not capable of sufficiently shielding the magnetic layers of adjacent tapes in such non-uniform pressure environments. Non-uniform pressure regions can propagate outward as the reel winds additional layers of tape. This is called lateral runout, and can result in significant data loss. One source of non-uniform pressure occurs in association with the buckle between the take-up leader and the supply leader used on single-reel data tape cartridges. For example, differences between the buckle and the thickness of the take-up leader or the supply leader may create regions of uneven pressure distribution, which may result in print through.
What is needed is a take-up reel configured to reduce print through errors on tape wound thereon by improving the circularity of the surface presented for winding data tape.
Accordingly, the present invention provides a take-up reel including a hub configured to improve circularity and thus reduce print through errors on tape wound thereon by allowing portions of the buckle to recess into the take-up reel. The particular configuration of the take-up reel may be adapted for use with a buckle configuration. A preferred embodiment of the take-up reel of the invention will be described for use on the buckle shown in FIG. 2. However, the invention could be easily adapted by one skilled in the art for use with other buckle configurations.
In one embodiment of the reel, the hub includes a circumferential peripheral surface with a circumference of the peripheral surface defined by a first radius. At least one raised ridge is formed on one portion of the peripheral surface of the hub with an outer surface of the ridge defined by a radius larger than the radius of the peripheral surface. The ridge preferably has a width less than the width of the peripheral surface, and includes a pair of grooves with a length perpendicular to the edge of the peripheral surface. Two flattened regions are preferably formed on each side of the ridge, meeting at a crest located at approximately the center of the arc of the ridge. The reel also preferably includes a take-up leader with apertures sized and positioned to accept the ridge or other structures on the peripheral surface of the hub.
As the buckle is wound onto the hub, at least one layer of take-up leader is preferably wound onto the peripheral surface of the hub between the buckle and the peripheral surface of the hub. Subsequent layers of tape wound thereover are supported by one or more of the following: (a) the previous layers of tape wound over the peripheral surface of the hub and the flattened regions, (b) the portions of the buckle recessed into the hub so that an outer surface of the buckle is approximately aligned with the outer surface of the ridge, (c) and the outer surface of the ridge itself. The layers of tape wound immediately over the supporting structures previously described are intended to present a surface that is highly circular for winding subsequent layers of magnetic tape, thus minimizing potential for print through as the tape is wound thereon.